The demonstration of gene transfer, mRNA and protein expression and biological efficacy is critical to the successful development of gene transfer vectors and pharmacologic therapies. An Expression Core has been in operation at Johns Hopkins University during the past budget period of the grant. This Core has considerable expertise in assaying for normal and defective function of CFTR by methods such as: 1. [36]Cl- efflux and more specific assays such as patch clamping; 2. evaluating gene transfer, mRNA expression, vector shedding and spread in animal and patients samples; 3. assaying for protein expression. Work from this Core during the previous budget period was instrumental in the identification of adenoviral and adeno-associated virus systems as potential therapeutic agents and also phenylbutyrate as a potential therapeutic. The recent development of gene transfer technologies as potential therapies and new pharmacologic therapies such as phenylbutyrate have increased considerably the demand for the services of our Expression Core. The Expression Core functions as both a research and development Core, and in addition provides support for the projects within this Gene Therapy Center.